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Analysing Market Structures

Efficiency across the market structures

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  • Unit A2 1

Overview

Allocative efficiency and state the condition that identifies it, perfectly competitive firm allocatively efficient in long-run equilibrium and monopoly achieve neither allocative nor productive efficiency.

What you need to know

Answer each one before you reveal it.

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Key term

What is dynamic efficiency, and how does it differ from productive and allocative efficiency?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define allocative efficiency and state the condition that identifies it.

    Model answer

    Allocative efficiency is reached when resources are distributed so that no reallocation could make anyone better off without making someone else worse off, which for a single market means output is at the level society values most. The condition is that price equals marginal cost. Price measures the value the marginal buyer places on the last unit and marginal cost measures the value of the resources used to make it, so equality means the last unit produced is worth exactly what it cost society.

  2. 2

    Define productive efficiency and state where it occurs on a cost curve diagram.

    Model answer

    Productive efficiency means output is produced at the lowest possible average cost, so no resources are wasted in making it. It occurs at the minimum point of the average total cost curve, which is also the point where the marginal cost curve cuts average total cost from below. A firm producing at any other output is using more resources per unit than it needs to.

  3. 3

    A firm has fixed costs of £60 and total variable costs of 40, 64, 78, 96, 130 and 186 at outputs of one to six units. At which output is it productively efficient?

    Model answer

    Total cost is 100, 124, 138, 156, 190 and 246, so average total cost is 100, 62, 46, 39, 38 and 41. The minimum is £38 at five units, so five units is the productively efficient output. The marginal cost figures confirm it: marginal cost is £34 at the fifth unit, below the £39 average, which pulls the average down, and £56 at the sixth, above the £38 average, which pushes it back up.

  4. 4

    A monopolist faces P = 100 − 2Q and has total costs TC = 30 + 10Q + Q². Show that its chosen output is not allocatively efficient, and find the output that would be.

    Model answer

    It produces where marginal revenue equals marginal cost: 100 − 4Q = 10 + 2Q gives Q = 15, P = £70. Marginal cost at that output is 10 + 2(15) = £40, so price exceeds marginal cost by £30 and the last unit is worth far more to buyers than it costs to make. Allocative efficiency requires price to equal marginal cost: 100 − 2Q = 10 + 2Q gives 90 = 4Q, so Q = 22.5 units at a price of £55. The monopolist therefore under-produces by 7.5 units.

  5. 5

    For a monopolist with demand P = 100 − 2Q and costs TC = 30 + 10Q + Q², calculate the deadweight welfare loss and describe the area it occupies on the diagram.

    Model answer

    The firm produces 15 units at £70, where marginal cost is £40; the allocatively efficient output is 22.5 units at £55, where price and marginal cost are both £55. The loss is the triangle bounded above by the average revenue curve, below by the marginal cost curve, and on the left by the vertical line at 15 units, closing at the point where the two curves meet at 22.5 units. Its vertical side runs from £40 to £70, a height of £30, and its horizontal base runs from 15 to 22.5 units, a length of 7.5. The area is ½ × 7.5 × 30 = £112.50.

  6. 6

    Why is a perfectly competitive firm allocatively efficient in long-run equilibrium?

    Model answer

    The firm's demand curve is horizontal at the market price, so marginal revenue equals price. It maximises profit where marginal cost equals marginal revenue, and therefore where marginal cost equals price. That is precisely the allocative efficiency condition, and it holds in the short run as well as the long run. What the long run adds is that entry has pushed price down to minimum average total cost, so the firm is productively efficient at the same time.

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Demand and Supply in Product Markets
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